dbcve.org
ZendtoApplication · Zend

CVE-2021-27888

MEDIUM · 6.1 CVSS v3.1 Published 2021-03-02
Fix available
A fix is available. Upgrade to after 6.05-4 or later.
See remediation →
68/100
Remediation priority · Elevated
Remotely reachable No privileges

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
ZendTo before 6.06-4 Beta allows XSS during the display of a drop-off in which a filename has unexpected characters.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · moderate confidence

ZendTo versions before 6.06-4 Beta suffer from a stored Cross-Site Scripting (XSS) vulnerability. The flaw occurs when displaying drop-off file information, where filenames containing unexpected or malicious characters are not properly sanitized or encoded before rendering in the web interface, allowing attackers to inject arbitrary JavaScript code.

MitigationUpgrade to ZendTo 6.06-4 Beta or later. As a temporary measure, ensure filenames are properly encoded/sanitized using context-appropriate output encoding before display to prevent script execution.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
ZendtoApplication
Affected:<= 6.05-4= 6.06-1= 6.06-2= 6.06-3

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
Required
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Locate ZendTo installation directory
    Identify the web server document root or PHP include path where ZendTo is installed. Common locations include /var/www/zendto, /opt/zendto, or within the web server's htdocs folder. Look for files such as version.php, CHANGELOG.txt, or README that contain version information.
    Affected if Unable to locate installation directory or version files
  2. Determine installed ZendTo version
    Open the version file or CHANGELOG in the ZendTo installation directory. Look for a version number displayed in files like 'version.php', 'changelog.txt', or the main index page source. Extract the exact version number (e.g., 6.05-4, 6.06-1, 6.06-3).
    Affected if Version cannot be determined or is not clearly displayed
  3. Compare version against affected ranges
    Verify if the installed version falls within: 6.05-4 or lower, OR exactly 6.06-1, 6.06-2, or 6.06-3. These versions are vulnerable. Versions 6.06-4 Beta and later are not affected.
    Affected if Installed version is <= 6.05-4 OR equals 6.06-1, 6.06-2, or 6.06-3
  4. Confirm drop-off file display is in use
    Access the ZendTo web interface as a user who can create or view drop-offs. Create a test drop-off with a file, or view an existing drop-off's file listing. The vulnerability affects the display of filenames in the drop-off information page.
    Affected if ZendTo drop-off functionality is enabled and accessible
  5. Inspect filename output for encoding
    If running an affected version, examine the web interface's HTML source when viewing drop-off file information. Check if filenames are rendered with proper HTML encoding (e.g., &lt; for <, &gt; for >, &quot; for "). Use browser developer tools or view page source to inspect filename elements.
    Affected if Filenames are displayed without HTML entity encoding and special characters appear as raw text

The environment is affected if ZendTo version is <= 6.05-4 or equals 6.06-1, 6.06-2, or 6.06-3 AND the drop-off file display feature is in use, with filenames rendered without proper HTML encoding.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

From vendor data
Upgrade available Upgrade to a release after 6.05-4
Interim mitigation

Upgrade to ZendTo 6.06-4 Beta or later. As a temporary measure, ensure filenames are properly encoded/sanitized using context-appropriate output encoding before display to prevent script execution.

Fix this in Zendto Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
11.0 hours of engineering $1,930
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,088.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-27888 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data